The present invention relates to metal casting and can be used in producing castings with directional and single crystal structure. In particular the invention relates to a metal casting apparatus with a water-cooled tank having a truncated cone shape.
An apparatus for directional solidification generally comprises a vacuum chamber inside which there are disposed a mold heating zone, a baffle system, a water-cooled chill plate usually made of copper, an induction furnace, and a thermocouple system that automatically controls and maintains the temperature in a cooling zone and in a heating zone within the furnace. Such features are disclosed in U.S. Pat. Nos. 3,680,625, 4,804,311, and 4,412,577.
Also known in the art is an apparatus for directional solidification, in which the cooling zone is a liquid cooling bath with a material that melts easily to serve the role of the cooling medium. The liquid metal bath is disclosed in U.S. Pat. Nos. 3,763,926 and 3,915,761, and Russian Federation Patent No. 2010672.
Apparatuses in which both types of the above mentioned assemblies are combined (i.e., the copper chill plate and the liquid metal cooling bath) are also known. But those apparatuses comprise two actuators for vertical transportation of a mold with a metal casting. These actuators are disposed above and beneath the vacuum chamber housing. For that reason the dimensions of the apparatuses are enlarged and the service of the installations become complicated while the reliability of the apparatuses is decreased (see U.S. Pat. No. 5,197,531, and the publication Singer R. F. xe2x80x9cDirectional and Single Crystal Solidification Using LMCxe2x80x9d).
The closest prior art to the embodiments of the present invention is an apparatus disclosed in French Patent Application 2604378. French Patent Application 2604378 discloses an apparatus comprising a vacuum chamber with a heating member inside where there is disposed a ceramic mold fixed on a water-cooled metallic plate which is moved up and down with the help of a rod and of an actuator for vertical transportation A horizontal baffle separates a heating zone and a cooling zone In the cooling zone concentrically with the chill plate, there is disposed an additional circular water-cooled cavity with the inner diameter exceeding the mold s maximal size. Below the cavity there is disposed a container that is utilized for capturing the poured casting metal in the event of mold breakage.
The above apparatuses, including the apparatus of French Patent Application 2604378, can function only when they comprise a crystallizer. It is impossible to use such installation for directional solidification processing with a liquid metal coolant and it is difficult to utilize the expensive alloys used in directional solidification castings in the event of mold breakage. Thus there is a need for a casting apparatus that provides a means that efficiently cools the molten cast alloy while protecting the equipment from damage in the event that the ceramic mold breaks while containing the molten cast alloy material.
The technical aim of this invention is to produce castings having the directional and single crystal structure by the method of radiation cooling without using the above-mentioned crystallizer. Another aim of the invention is to be able to reconstruct easily the invented apparatus for both radiation crystallization processing and liquid metal cooling crystallization processing. The inventive apparatus also increases the reliability and economic profit due to the apparatus"" performance.
An embodiment of the apparatus comprises a vacuum chamber inside which there is disposed an induction melting furnace a mold preheating furnace with a ceramic mold, a drive assembly for mold transportation and a water-cooled tank. The drive assembly comprises a rod on which the mold is fixed with the help of a hanger and a regulating actuator for vertical movement being positioned above the vacuum chamber. The water-cooled tank is shaped as a truncated cone. The tank upper portion is opened towards the heating zone, and its bottom portion has a smaller base than the upper portion. A baffle separates the heating zone inside the induction furnace from the cooling zone. The baffle moves in a horizontal plane and closely adjoins the mold during the solidification process. The baffle consists of the segments or sectors (not less than 2 from each side).